1. Field of the Invention
The present invention relates to the field of telecommunications and, more particularly, to a detection and a notification of an off-hook telephone event.
2. Description of the Related Art
Telephones are often left off the hook by mistake, thereby preventing incoming calls from being received. Even though telephony companies monitor for off-hook telephones and responsively convey an off-hook tone to unattended telephones, a telephone user can remain unaware of the off-hook event. For example, the volume of the telephone receiver can be relatively low so that the off-hook tone is not heard. Another reason the off-hook tone can remain unheard is that the telephone user could no longer be proximately located to the off-hook telephone. Conventional devices do not provide an adequate solution to the detection and notification of off-hook events.
Prior art on/off-hook detection and notification devices involve the monitoring of the voltage differential existing within a circuit loop. The voltage differential (between the “tip” and “ring” telephone wires) is generally equal to the central office (telephony switch) battery voltage less some small amount attributable to resistance losses, which is typically in the range of −40 to 47 volts Direct Current (DC). When an off-hook condition occurs, a current is drawn from the circuit loop resulting in a voltage drop in the circuit loop of approximately 10 to 15 volts DC. Additional off-hook telephony devices in the circuit loop can result in an additional voltage drop of typically 1 to 3 volts DC per additional device.
Monitoring for voltage differential to detect off-hook events at the central office (telephony switch) involves the telephony company implementing customized hardware and software solutions. When a telephone company or value-added service provider provides additional off-hook notification services via Fax or email (as indicated in U.S. Pat. No. 6,453,017 B1), these services can entail a monthly surcharge that the majority of users may be unwilling to pay. Further, the notification services can be limited to areas serviced by particular providers using particular telephony equipment.
Monitoring for voltage differential to detect off-hook events using customer premise equipment (CPE) can require an investment in expensive hardware designed specifically for the detection of off-hook events based on voltage drops. Few users are willing to incur the expense of dedicated CPE to detect and/or provide notice of off-hook events. Consequently, a method of monitoring and notifying users of off-hook events that users can implement without purchasing dedicated CPE is needed.